Method and apparatus for fissuring fibrous materials



p 13, 1955 J. D. ALEXANDER 2,717,538

METHOD AND APPARATUS FOR FISSURING FIBROUS MATERIALS Filed Jan. 15, 1955 INVENTOR ATTORNEY JOHN D. ALEXANDER United States Patent') METHOD AND APPARATUS FOR FISSURING FIBRGUS MATERIALS John D. Alexander, Beaver Falls, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvmria Application January 15, 1953, Serial No. 331,426

3 Claims. (Cl. 92-39) This invention relates to a method and apparatus for forming a fissured building unit and more particularly to a method and apparatus for forming a fibrous building unit such as an acoustical tile with fissures extending to a substantial depth from the surface thereof.

An acoustical material which has high sound-absorption properties is made from a water slurry of mineral wool fibers and a binder such as starch, the slurry being deposited continuously upon a moving wire screen and the water removed by drainage and suction. The mat thus formed is dried and the binder set, after which the mat is cut into units of desired dimensions for installation. In order to improve the appearance of the product and enhance its sound-absorption properties, the wet mat is frequently fissured to provide an open surface resembling travertine marble. This may be accomplished by the use of a fissuring board provided with pins which are pressed into the surface of the wet mat, and then the board is moved relative to the mat, generally diagonally of the length thereof, to disrupt the mat and form fissures. This is commonly a hand operation performed during movement of the mat from the forming station to the drier.

An object of the present invention is to provide an apparatus for fissuring which may be combined with conventional forming equipment to fissure a partially dewatered mat, prior to final drying.

Another object of the invention is to provide a method and apparatus for fissuing which may be used with con ventional forming equipment without interfering with the normal operation of such equipment and without necessitating any reduction in thespeed thereof.

A further object of the invention is to provide a method and apparatus for fissuring which will provide fissures which extend to a substantial depth below the exposed surface of the unit, the fissures being randomly disposed and, if desired, the various units being of a substantially uniform character as contrasted with conventional hand fissuring where one unit may have large and deep fissures and the next day may be of an entirely different character with practically all small fissures.

An additional object of the invention is to provide a method and apparatus for fissuring which will operate on a continuously moving water-laid web of fibrous material in partially dewatered condition.

Other objects of the invention will become apparent from consideration of the following description of the invention.

This invention is based on the discovery that a substantially smooth, curved surface if pressed into engagement with a partially dewatered, water-laid mass and relative movement effected between the surface and mass will result in the formation of fissures in the mass which extend a substantial distance into the mass from the surface thereof. The preferred fissuring surface is a roll which is pressed into engagement with the partially dewatered mass as it is moving from the forming station to the drying station, with the roll rotating in the ice direction of travel of the mass, but at a slower surface speed.

A preferred embodiment of the invention will bedescribed in conjunction with the attached drawing, in which:

Figure 1 is a diagrammatic view of the apparatus of the invention; and

Figure 2 is a plan view of a piece of the fissured product resulting from use of the apparatus and practice of the method of the invention.

Referring to Figure 1 there is shown an arrangement for forming a water-laid web including a wire forming screen 2 above which is disposed a hopper 3 for the reception of a water slurry of mineral wool fibers, for example, and a binder such as starch. A conventional Fourdrinier or a modified cylinder machine or other apparatus for forming a water-laid web may be employed. The mat 4 formed on the screen 2 is confined along its longitudinal edges by deckle belts 5, and Water is drained through the screen 2 as it moves the mass from the forming station at the hopper 3 toward a drying oven as indicated in Figure 1. A conventional suction box, diagrammatically illustrated at 6 in Figure 1, may be provided for removing additional water from the mass prior to passage into the drying oven.

interposed between the forming station and the drying oven is a fissuring station where the partially dewatered mat is operated upon by a fissuring roll 7 mounted transversely of the machine and disposed for. engagement with the mat 4. The fissuring roll 7 is diagrammatically illustrated as driven by a motor 8 through a gear reduction unit 9, the output shaft of which is connected by a sprocket and chain drive 10 to the roll 7. The roll 7 is preferably mounted in adjustable supports and is movable toward and away from the screen 2 to accommodate mats of dilferent thicknesses and to vary the amount of compression of the mat during fissuring. The character of fissuring will vary according to the consistency of the partially dewatered mat, the amount of reduction in thickness of the mat efiected by the fissuring roll, the nature of the fibrous material being operated upon, the amount of relative motion between the fissuring roll and mat, the thickness of mat to be fissured, and other variable factors.

As a typical example, in the production of an acoustical unit made up principally of mineral wool fibers and a starch binder having a finished thickness of the mass deposited on the wire 2 may initially be about 1%" thick in the zone 11 in advance of the fissuring roll 7. The initial slurry may contain about 20% solids by weight, and a substantial quantity of water will be drained through the screen 2 as the mass'moves frornthe forming station at hopper 3 toward the zone of the fissuring roll. The fissuring roll will be positioned at the desired location along the path of travel of the wire 2 to obtain the desired fissuring which, as mentioned above, will vary with the consistency of the partially dewatered mat. In the embodiment illustrated the mat will contain about 30% solids and of water by weight at the time of fissuring. The lineal speed of the wire screen 2 may be about 39" per minute. The fissuring roll 7 may be about 8" in diameter and travelling at about 26" per minute in the direction of the arrow shown in Figure 1. Thus the relative motion between the roll surface and the mat surface in engagement therewith is in the order of 13" per minute.

The mat may be reduced in thickness at the fissuring roll by about (It has been exaggerated in the drawing.) The relative motion between the curved surface of the fissuring roll and the surface of the mat and the frictional drag of the wet mass results in the creation of deep fissures in the mass extending from the upper surface toward the screen. A small pool of the slurry may build up behind roll 7 as indicated at 12 in Figure 1. The fissured mass then moves over the suction box 6 Where additional water is removed, and the mass is reduced to a thickness of about 1. The mass then goes to a drying oven where the product is reduced to the desired state of dryness and the binder is activated. After drying, the product is preferably sanded or otherwise severed on its upper surface to provide the desired smoothness and to remove any thin crust which may have formed over the fissures, particularly the smaller ones, during the suction operation and oven drying. This may reduce the mat to a thickness of which is mentioned above as the desired final thickness for the finished product. The mat may then be severed into units of the desired dimensions, for instance, tiles 12" x 12 square. The foregoing constitutes a single example of the practice of the method of this invention in the formation of a fissured mineral wool soundabsorbing tile 12" x 12 X The invention will be generally useful in forming fissured products of various sorts and sizes for many uses.

The roll 7 while preferably of metal having an essentially smooth surface may be formed with a resilient surface layer such as a rubber-covered roll. The diameter may vary from the 8" diameter roll mentioned above, depending upon the character of fissuring desired; for instance, a roll 6 in diameter will form a different character of fissuring than a 12" diameter roll.

Figure 2 illustrates a portion of a finished unit. It will be noted that it includes fissures 13 of irregular shape and size distributed over the whole extent of the upper surface of the unit. These fissures extend throughout a substantial portion of the thickness of the unit.

From the description of an embodiment of the invention given above it will be clear that the fissuring may be accomplished on a partially dewatered mat delivered from any water-laid web-forming unit, including a conventional Fourdrinier machine, and that since the curved fissuring surface may be in the form of a roll rotating in the direction of movement of the mat to be fissured, the fissuring may be accomplished at the speed of mat formation. Also, the fissures while being mechanically formed will be of nonuniform shape and size but will be of a substantially uniform character over-all in the sense that the fissuring in one portion of a run of the machine will not differ greatly in character from a preceding or succeeding portion of the run if the variable factors mentioned above are held constant. However, fissuring of widely differing character may be produced from run to run by changing the relative motion between the fissuring surface and the mat surface, by altering the consistency of the partially dewatered mat, or by changing others of the variable factors mentioned.

I claim:

1. A method of forming fissures extending to a substantial depth from the surface of a mineral fiber mat, the steps comprising drawing a partially dewatered waterlaid Web of mineral fiber material in the form of a wet mat into engagement with and under a rotating fissuring roll which is driven to move in the direction of travel of said mat at a slower speed than the speed of travel of said mat, compressing said mat by said fissuring roll as the mat moves thereunder, and building up a body of slurry to the rear of said fissuring roll while drawing said mat under said fissuring roll to form fissures which extend into the mat to a substantial depth from the surface thereof.

2. A method of forming fissures extending to a substantial depth from the surface of a mineral fiber mat, the steps comprising depositing upon a moving foraminous web a slurry of mineral fibers, water, and a binder; partially dewatering said slurry during motion thereof to form a wet mat; drawing said partially dewatered waterlaid mat of mineral fiber material into engagement with and under a rotating fissuring roll having a smooth surface which is driven to move in the direction of travel of said mat at a slower speed than the speed of travel of said mat; compressing said mat by said fissuring roll as the mat moves thereunder; building up a body of slurry to the rear of said fissuring roll while drawing said mat under said fissuring roll to form fissures which extend into the mat to a substantial depth from the surface thereof; drying said mat which forms a crust over some of said fissures; and severing the surface of the mat subsequent to drying thereof to expose the inner fibrous portion of the mat in the fissured surface.

3. An apparatus for forming fissures extending to a substantial depth from the surface of a mineral fiber mat comprising: a water pervious conveyor for the reception of a slurry of mineral fibers and through which water may pass to partially dewater said slurry and form a mat therefrom, means for progressing said conveyor while partially dewatering said slurry, a substantially smooth fissuring roll interposed along the path of travel of said conveyor for engagement with said partially dewatered slurry to compress the same as it moves under said fissuring roll, and means for rotating said fissuring roll in the direction of travel of said conveyor at a slower speed than the speed of travel of said conveyor to form fissures which extend to a substantial depth from the surface of and into said mat as it is compressed and moved under said fissuring roll.

References Cited in the file of this patent UNITED STATES PATENTS 992,693 Smith et a1. May 16, 1911 992,695 Smith et al May i6, 191] 2,154,201 Frost Apr. ll, I939 2,225,585 Devereux Dec. 17, 1940 

3. AN APPARATUS FOR FORMING FISSURES EXTENDING TO A SUBSTANTIAL DEPTH FROM THE SURFACE OF A MINERAL FIBER MAT COMPRISING: A WATER PREVIOUS CONVEYOR FOR THE RECEPTION OF A SLURRY OF MINERAL FIBERS AND THROUGH WHICH WATER MAY PASS TO PARTIALLY DEWATER SAID SLURRY AND FORM A MAT THEREFROM, MEANS FOR PROGRESSING SAID CONVEYOR WHILE PARTIALLY DEWATERING SAID SLURRY, A SUBSTANTIALLY SMOOTH FISSURING ROLL INTERPOSED ALONG THE PATH OF TRAVEL OF SAID CONVEYOR FOR ENGAGEMENT WITH SAID PARTIALLY DEWATERED SLURRY TO COMPRESS THE SAME AS IT MOVES UNDER SAID FISSURING ROLL, AND MEANS FOR ROTATING SAID FISSURING ROLL IN THE DIRECTION OF TRAVEL OF SAID CONVEYOR AT A SLOWER SPEED THAN THE SPEED OF TRAVEL OF SAID CONVEYOR TO FORM FISSURES WHICH EXTEND TO A SUBSTANTIAL DEPTH FROM THE SURFACE OF AND INTO SAID MAT AS IT IS COMPRESSED AND MOVED UNDER SAID FISSURING ROLL. 